880 J. E. MARK ON LIFE-ZONES OF THE 



c Pah Shales. — These beds have been stated by Profs. Harkness 

 and Nicholson (Quart. Journ. Geol. Soc. vol. xxxiii. p. 478) to present 

 more affinities with the Coniston Flags than with the Graptolitic 

 Mndstones. I see no reason, however, to depart from the view held 

 by the Geological Survey, that they are more closely related to the 

 Graptolitic Mudstones. They are very similar in lithological cha- 

 racter, if we omit the Graptolitic beds themselves, which are probably 

 in great part due to the Graptolites. 



Of the fossils, Mcnograptus lobiferus occurs well up in the Pale 

 Shales, in a thin mudstone band on Applethwaite Common. More 

 highly organized fossils also occur in the Pale Shales. Profs. Hark- 

 ness and Nicholson mention some from the high ground between 

 Troutbeck and Skelgill ; and I have found here a small brachiopod, 

 apparently a Meristella. In the Woodwardian Museum there are 

 two specimens of StricMandinia lirata, Sow., occurring in one block 

 from the Pale Shales of Rebecca Hill, near Ulverston. 



On comparing the fossils of the basement-bed and of the Stock- 

 dale Shales with those of the Coniston Limestone and Ashgill Shales, 

 we find very few fossils common to the two series. Favositesjibrosus, 

 Leptcena quinquecostata, Strophomena siluriana, and Oheirurus bi~ 

 mucronatus are the only species found in both ; and of these, Favosites 

 fibrosus is a species having an enormous range, whilst Leptcena quia- 

 quecostata and Cheirurus bimucronatus are very rare in the Coniston 

 Limestone, although abundant in the Stockdale series. Stropliomena 

 siluriana, on the other hand, abounds in the Ashgill Shales, nnd 

 occurs in one locality, in no great abundance, in the basement-bed. 



It appears from the above conclusion that the position of the 

 boundary between the Cambrian and Silurian rocks must be re- 

 ferred to the same horizon, whether we determine it from 

 physical or palaeontological evidence. Not only is there a palsBon- 

 tological break between the Ashgill Shales and what has been taken 

 as the basement-bed of the Silurian, but whereas in the Ashgill 

 Shales and underlying beds we get a group of fossils agreeing in all 

 respects with those of the Cambrian series of other districts, in the 

 beds above the Ashgill Shales we find a well-marked Silurian fauna, 

 which will probably be largely added to in future. 



5. Coniston Flags. 



In the Windermere district an excellent section of these beds is 

 seen in the neighbourhood of the well-known Coldwell and Brathay 

 quarries, situated on the west side of Windermere Lake, about two 

 miles S.W. of Ambleside. They are seen to consist of two well- 

 marked divisions, easily separable by lithological characters. The 

 lower division consists of blue, well-cleaved, and finely laminated 

 flags, of uniform lithological character throughout, and of exceed- 

 ingly fine texture. This division makes up about a third of the whole 

 thickness of the Coniston Flags. Above these blue flags we find a 

 series of gritty beds, all somewhat similar, but separable into three 

 distinct subdivisions, forming the remainder of the Coniston-flag 

 series. These subdivisions are : — (a) a lower series of coarse grey 



